Experimental Study of the Stretch Flange Formability of Al-Mg Sheet

Abstract:

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In this paper, stretch flange forming experiments were performed on the AA5182 and
AA5754 Al-Mg sheet materials. A triple-action servo-hydraulic press, developed at the University
of Waterloo, was used in the experiments. A z-flange tooling, which incorporates mating drawbeads
on the main and backup punches, was employed. Drawbeads are used in commercial stretch flange
operations to control or limit the rate of cutout expansion. Of interest in the current research are the
flange formability and the damage development induced by the bending-unbending of the sheet as it
passes through the drawbeads. Both AA5182 and AA5754 were tested with thickness of 1.6 mm.
Further tests were performed using 1.0 mm AA5182 to examine the effect of thickness. To examine
the effect of cutout size on the formability, cutout radii in the range 88 to 98 mm in increments of 2
mm were tested to failure.

Abstract: In this paper, the forming limit of flange in radial extrusion process was analyzed by the
rigid-plastic finite element method. The selected model material for simulation and experiments was
AA 3105 aluminum alloy. The predictions from simulation were made in terms of axial and
circumferential strains. Experiments also have been conducted to compare with the simulation results
with regards to deformation pattern. Furthermore, the deformation pattern in forming of flange
section was closely investigated and categorized in three cases such as sticking, separating and
cracking. The analysis in this paper is focused on the transient extrusion process of material flow into
the gap in radial direction for different gap heights and die corner radii. The results of present study
were summarized in terms of evolution of surface strains in axial and circumferential directions
measured from the finite element meshes located in the region where surface cracking occurred in
experiments. The forming limit line was drawn in the relationship of circumferential and axial strain.
It was concluded from this study that the forming limit line is influenced mainly by circumferential
strain on free surface of flange. It was also predicted that ductile fracture on flange surface is likely to
occur in the middle of flange gap under the condition of sticking deformation and near bottom of
flange gap under the condition of separating deformation, respectively. The forming limit of flange in
terms of flange diameter was expected about 2.5do, which is 2.5 times the diameter of original billet.

Abstract: In the paper, the interface crack of rubber - metal ring under the radial displacement load was studied by nonlinear finite element method, changes of the tear energy with crack dimension which extending from extrusion end and tensile end along the axial and circumferential direction to the interface was analyzed. The result is that there is a certain possibility of axial extension in the tensile end. The crack propagation is most likely to occur along the circumferential direction while is impossible along either axial or the circumferential direction in the extrusion end

Abstract: Cross wedge rolling hollow shafts with a mandrel has attracted much attention in the recent years because of the demand for light components. Finite element method was used to simulate the rolling process of hollow part and validated by experiment. By tracking strain change of the typical points and analyzing the strain contour maps of cross-section at four typical moments, the cause of cross section oval and shaft shoulder protuberance of part is expounded.

Abstract: Compression performance of pultruded GFRP (Glass Fiber Reinforced Plastics) can be improved by confined CFRP (Carbon Fiber Reinforced Plastics) sheet, but it was affected by some factors. Two groups GFRP short pipe specimens of different outer diameter (104mm and 76mm) were axial compressed. The failure modes of longitudinal splitting and compressive strength failure for the GFRP pipes and those confined by CFRP sheet respectively were comparatively analyzed. Analysis on the influence to the compressive performance of GFRP short pipes confined by CFRP sheet was made from mechanical and geometrical parameters of the CFRP and GFRP in numerical methods. The laws of improvement of compression performance of CFRP sheet confined GFRP short pipe were recognized.

Abstract: Strain localization in low carbon steel DC04 undergoing uniaxial tension is investigated by Electronic Speckle Pattern Interferometry (ESPI). The necking in the sheet specimens occurs by forming two narrow crossing bands. A model of strain rate distribution is used to extract quantitative information about the localization bands, such as bandwidths, bands orientations and their maximum strain rates. Thus, their evolutions are followed from the diffuse necking up to the rupture. The influence of specimen geometry on localization phenomenon is studied.